Cornscala Crossovers

[tubesandhorns]

Some questions about crossovers:

1) There are several excellent crossovers offered for Cornscala type speakers,

but much flexibility on the drivers- Seleium, BMS, etc. Don’t the crossovers have to match the complex

impedance characteristics of the specific driver? I assumed that at this level of performance the two need to be carefully matched.

2) I see references to changing taps on the autotransformer

to match levels. Doesn’t this change the impedance as seen by the crossover,

and therefore the corner frequency

3) While we’re at it, why autotransformers and not resistive

L-pads?

Thanks for any insights.

[MechMan]

If I remember correctly the use of the autoformer over an L pad is because the autoformer will not change the impedance load, while the L pad will.

About the X-overs yes...they will need to be matched to the drivers used, but I assume in the Klipsch community we all try to stick to certain drivers that work well together.

I'm sure someone can give you a more techy answer, mine is just what I have learned from hanging around here reading.

[Guest David H]

There are several excellent crossovers offered for Cornscala type speakers, but much flexibility on the drivers- Seleium, BMS, etc. Don’t the crossovers have to match the complex impedance characteristics of the specific driver?

Yes, however several of the drivers chosen by form members are a close enough match to be used as a direct replacement. Other drivers can be used, however require either a crossover modification or a network less effected by impedence changes. The networks from ALK use swamping resistors on the autoformer to stabilize the impedence seen by the network.

I see references to changing taps on the autotransformer to match levels. Doesn’t this change the impedance as seen by the crossover

Yes.

While we’re at it, why autotransformers and not resistive L-pads?

Good question, I have used both Lpads and autoformers, an noticed little to no differences, however the autoformer used in the Klipsch networks serve to attenuate both the tweeter and the squalker unlike the L-pad. The autoformer also allowed PWK to use smaller value capacitors in his netork, and offers better dampening characteristics than the resistive element of the Lpad.

The Lpad is basically a fixed impedence regaurdless of attenuation where the T2A autoformer doubles the impedence with each tap.

For more info,you may want to look at Al Klappenbergers site. www.alkeng.com

[MechMan]

I always thought it was impedance that was the benifate of the autoformer...I guess I need to leave it to the pro's.